Multi-Container Pods

Updated Dec 29, 2023 ·

Some of the scenario questions here are based on Kodekloud's CKAD course labs.

NOTE

CKAD and CKA can have similar scenario questions. It is recommended to go through the CKA practice tests.

Shortcuts

First run the two commands below for shortcuts.

export do="--dry-run=client -o yaml" 
export now="--force --grace-period=0"

Questions

Create a multi-container pod with 2 containers. Use the spec given below. If the pod goes into the crashloopbackoff then add the command sleep 1000 in the lemon container.

Name: yellow
Container 1 Name: lemon
Container 1 Image: busybox
Container 2 Name: gold
Container 2 Image: redis

Answer

controlplane ~ ➜  k run yellow --image busybox $do > yellow.yml

controlplane ~ ➜  ls -l
total 8
drwxr-xr-x 3 root root 4096 Jan  5 09:40 elastic-search
-rw-r--r-- 1 root root  237 Jan  5 09:43 yellow.yml 

## yellow.yml 
apiVersion: v1
kind: Pod
metadata:
  creationTimestamp: null
  labels:
    run: yellow
  name: yellow
spec:
  containers:
  - image: busybox
    name: lemon  
  - image: redis
    name: gold
    resources: {}
dnsPolicy: ClusterFirst
restartPolicy: Always
status: {}

controlplane ~ ➜  k apply -f yellow.yml 
pod/yellow created

controlplane ~ ➜  k get po
NAME        READY   STATUS              RESTARTS   AGE
app         1/1     Running             0          5m2s
blue        2/2     Running             0          3m30s
fluent-ui   1/1     Running             0          5m3s
red         3/3     Running             0          4m50s
yellow      0/2     ContainerCreating   0          3s 

Update the newly created pod 'simple-webapp-2' with a readinessProbe using the given specs:

Pod Name: simple-webapp-2
Image Name: kodekloud/webapp-delayed-start
Readiness Probe: httpGet
Http Probe: /ready
Http Port: 8080

controlplane ~ ➜  k get po
NAME              READY   STATUS    RESTARTS   AGE
simple-webapp-1   1/1     Running   0          2m7s
simple-webapp-2   1/1     Running   0          111s 

Answer

controlplane ~ ➜  k get po simple-webapp-2 -o yaml > simple-webapp-2.yml

controlplane ~ ➜  k delete po simple-webapp-2 $now
Warning: Immediate deletion does not wait for confirmation that the running resource has been terminated. The resource may continue to run on the cluster indefinitely.
pod "simple-webapp-2" force deleted

controlplane ~ ➜  k get po
NAME              READY   STATUS    RESTARTS   AGE
simple-webapp-1   1/1     Running   0          3m5s

controlplane ~ ➜  ls -l
total 16
-rwxr-xr-x 1 root root  114 Dec  1 06:17 crash-app.sh
-rwxr-xr-x 1 root root  216 Dec  1 06:17 curl-test.sh
-rwxr-xr-x 1 root root  123 Dec  1 06:17 freeze-app.sh
-rw-r--r-- 1 root root 2772 Jan  5 09:56 simple-webapp-2.yml 

Modify the YAML file.

apiVersion: v1
kind: Pod
metadata:
  creationTimestamp: "2024-01-05T14:53:47Z"
  labels:
    name: simple-webapp
  name: simple-webapp-2
  namespace: default
  resourceVersion: "631"
  uid: 302ac3b8-bb0b-4294-89dd-4eef603bf001
spec:
  containers:
  - env:
    - name: APP_START_DELAY
    value: "80"
    image: kodekloud/webapp-delayed-start
    imagePullPolicy: Always
    name: simple-webapp
    readinessProbe:
      httpGet:
        path: /ready
        port: 8080

controlplane ~ ➜  k apply -f simple-webapp-2.yml 
pod/simple-webapp-2 created

controlplane ~ ➜  k get po
NAME              READY   STATUS              RESTARTS   AGE
simple-webapp-1   1/1     Running             0          6m37s
simple-webapp-2   0/1     ContainerCreating   0          8s 

Update both the pods with a livenessProbe using the given spec

Pod Name: simple-webapp-1
Image Name: kodekloud/webapp-delayed-start
Liveness Probe: httpGet
Http Probe: /live
Http Port: 8080
Period Seconds: 1
Initial Delay: 80
Pod Name: simple-webapp-2
Image Name: kodekloud/webapp-delayed-start
Liveness Probe: httpGet
Http Probe: /live
Http Port: 8080
Initial Delay: 80
Period Seconds: 1

controlplane ~ ✦ ➜  k get po
NAME              READY   STATUS    RESTARTS   AGE
simple-webapp-1   1/1     Running   0          9m15s
simple-webapp-2   1/1     Running   0          2m46s 

Answer

controlplane ~ ✦ ➜  k get po simple-webapp-1 -o yaml > simple-webapp-1.yml

controlplane ~ ✦ ➜  k get po simple-webapp-2 -o yaml > simple-webapp-2.yml

controlplane ~ ✦ ➜  k delete po simple-webapp-1 $now
Warning: Immediate deletion does not wait for confirmation that the running resource has been terminated. The resource may continue to run on the cluster indefinitely.
pod "simple-webapp-1" force deleted

controlplane ~ ✦ ➜  k delete po simple-webapp-2 $now
Warning: Immediate deletion does not wait for confirmation that the running resource has been terminated. The resource may continue to run on the cluster indefinitely.
pod "simple-webapp-2" force deleted

controlplane ~ ✦ ➜  k get po
No resources found in default namespace. 

Modify the first pod first.

apiVersion: v1
kind: Pod
metadata:
  creationTimestamp: "2024-01-05T14:53:31Z"
  labels:
    name: simple-webapp
  name: simple-webapp-1
  namespace: default
  resourceVersion: "605"
  uid: 5843cf05-165d-4f4c-9293-21f21e9a7905
spec:
  containers:
  - image: kodekloud/webapp-delayed-start
    imagePullPolicy: Always
    name: simple-webapp
    livenessProbe:
      initialDelaySeconds: 80
      periodSeconds: 1
      httpGet:
        path: /live
        port: 8080
    ports:
    - containerPort: 8080
      protocol: TCP
    resources: {}
    terminationMessagePath: /dev/termination-log
    terminationMessagePolicy: File
    volumeMounts:
    - mountPath: /var/run/secrets/kubernetes.io/serviceaccount
    name: kube-api-access-zwmnp
    readOnly: true

controlplane ~ ✦ ➜  k apply -f simple-webapp-1.yml 
pod/simple-webapp-1 created

controlplane ~ ✦ ➜  k get po
NAME              READY   STATUS    RESTARTS   AGE
simple-webapp-1   1/1     Running   0          51s

Next, modify the YAML file for the second pod.

apiVersion: v1
kind: Pod
metadata:
  creationTimestamp: "2024-01-05T15:00:00Z"
  labels:
    name: simple-webapp
  name: simple-webapp-2
  namespace: default
  resourceVersion: "1286"
  uid: cfdd23e3-e7e3-4be7-9dd9-b2abf5f0ad0e
spec:
  containers:
  - env:
    - name: APP_START_DELAY
    value: "80"
    image: kodekloud/webapp-delayed-start
    imagePullPolicy: Always
    name: simple-webapp
    livenessProbe:
      initialDelaySeconds: 80
      periodSeconds: 1
      httpGet:
        path: /live
        port: 8080
    ports:
    - containerPort: 8080
      protocol: TCP
    readinessProbe:
      failureThreshold: 3
      httpGet:
        path: /ready
        port: 8080
        scheme: HTTP
        periodSeconds: 10
    successThreshold: 1
    timeoutSeconds: 1
    resources: {}
    terminationMessagePath: /dev/termination-log
    terminationMessagePolicy: File
    volumeMounts:
    - mountPath: /var/run/secrets/kubernetes.io/serviceaccount
    name: kube-api-access-xvbr6
    readOnly: true

controlplane ~ ✦ ➜  k apply -f simple-webapp-2.yml 
pod/simple-webapp-2 created

controlplane ~ ✦ ➜  k get po
NAME              READY   STATUS    RESTARTS   AGE
simple-webapp-1   1/1     Running   0          118s
simple-webapp-2   0/1     Running   0          6s

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